1. Field of the Invention
This invention relates to a tire testing facility for testing tires and a method for testing tires with such tire testing facility.
2. Description of Related Art
Methods for testing tires are known already. It is particularly advantageous to test the tires by interferometry. Interferometric testing is a relative testing method, in which the surface contour of the tire in two or more different conditions is compared with each other. Typically, the tire undergoes a load change between the individual conditions, which effects a significant change in the surface contour at defective points. The load change in particular is a change in the ambient pressure. By means of the change in the surface contour defects in the tire can be inferred.
Proceeding therefrom, care should be taken in the interferometric test that a change in contour which is not due to the load change is avoided. In the commonly used testing systems, this can for instance be achieved by a rather vibration-insensitive assembly, which prevents disturbances and changes in the position of the measuring head and/or the tire. Moreover, tensions and creeping movements in the tire can be suppressed by a stable support of the tire.
Excessive self-movements of the tire lead to great malfunctions in the final analysis up to an exceedance of the measurement range of the interferometric measurement. Therefore, rigid specimens are more suitable for interferometric tests than tires which are slow to respond to changes in force and slowly change their shape over a period of minutes even up to hours.
In commonly used interferometric testing devices, tires therefore are tested without rim and lying on a sidewall, in order to ensure a rather full-surface support and thus minimize vibrations and self-movements. In this position, at least one testing head tests the whole tire portion by portion, wherein the running surface can be tested from inside in individual sectors and bead and sidewall can be tested from outside.
From EP 1 043 578 A2, an optical testing device for tires is known, which comprises a plurality of laser measuring heads.
EP 1 284 409 A1 discloses an apparatus for examining tires with an interferometric measuring head and with a light-section contour detection system for generating light surfaces, which are oriented towards a camera such that the light sections generated on the tire can be observed with the camera.
From EP 1 355 142 A2, a tire testing device is known, which includes horizontal rollers on which the tire can be positioned in a vertical position.
In the prior art tire testing devices, the testing head is circumferentially moved relative to the tire, in order to successively test first the entire running surface and in a second cycle the first sidewall. Thereafter, the tire must be lifted and turned over, so as to be able to also test the second sidewall in a third cycle.
According to EP 1 355 142 A2, this disadvantage is overcome in that the tire is tested in the upright position, so that both sidewalls of the tire can be tested without the tire having to be turned over. For testing the tire, one portion each is tested. Thereafter, rotating the tire is continued, so as to be able to examine the whole tire in this way. For rotating the tire, rollers are provided, which support the tire on its running surface or in the rim hole. However, the tire each experiences non-uniform forces, which can lead to dents and whole-body deformations. Before the interferometric test, it must be waited for these disturbances to subside. After each rotation of the tire for testing the next portion, new force relations exist, which can in part lead to waiting times lasting several minutes.
Further tire testing devices are known from DE 103 19 099 B4, DE 689 22 855 T2, DE 10 2006 015 123 A1, DE 42 32 201 A1, EP 1 808 686 A1, EP 1 500 917 A2 and US 2005/0058333 A1.